Ook’s Worm Bin: Final Report on the Vermicomposting Project

The worm bin was started in the library in April 2017 with a handful of worms. Over the course of a year the worms increased and we harvested the compost several times. They were given mostly banana peels, apple cores, teabags, and old peppers and tomatoes. We used damp, shredded newspaper for bedding. The fruit and vegetable matter was always frozen for a few days first to make sure we didn’t get fruit flies in the bin. They were also given eggshells. Compost was harvested every couple of months, but the bin was never entirely cleared out; we just did partial harvests.

Worms were taken out to start four other bins for the 4-H group.

Problems we had:

We had a lot of mites in the worm bin, especially when it was wetter. Once the worms all tried to flee the bin, because we gave them crumbled-up old cake and it grew a lot of blue mould. Worms are supposed not to mind some mould, but obviously they do!

Another time the worms were given too many leftover green peas from the restaurant. A week later, the bin smelt like a pig-sty! (Have you ever smelt a pig-sty? Pig manure is very high in ammonia. It stinks!)

Solutions we tried:

In the fall of 2017 we put some dry leaves on top of the compost in the bin. We noticed that the population of mites seemed to drop. The leaves stayed dry on top while the compost underneath was moist. In the winter we started using newspaper again, and the mites reappeared.

When the worms all tried to crawl out, we picked out the mouldy cake and gave them a lot of new damp-newspaper bedding.

When we ended up with a stinky bin because of too many cooked green peas, we had to take out the peas and a lot of the newspaper, prepare new bedding and food, and air out the worm bin and the library.

The worms go home:

In April of 2018 the worm bin was taken to the library manager’s house, because the library gets very hot on sunny days in the summer. In her cellar the temperature is about 12 to 15 degrees Celsius all year round. The worms seemed happy in the cellar and didn’t try to crawl out. They were fed only about once a week, with fruit waste (frozen), eggshells, and vegetable peelings. There were still mites in the bin.

In May, after harvesting some compost, the library manager put a lot of dead leaves (mostly maple) in as bedding.

In June, the library manager noticed that there seem to be no mites in the worm bin, although underneath the surface leaves the compost is quite moist. Since last time that happened was when she put leaves in when the bin was at the library, where it is warmer, it seems likely that using dry leaves as bedding is what reduces the mite population, not the temperature or the moisture content.

There was also a small spider living in the bin, and a few sowbugs. (It’s likely that the sowbug came in with the leaves, since the cellar is fairly dry. The spider could not have eaten all the mites.)

Observations and Conclusions:

Dry leaves may be better worm bin bedding than shredded newspaper. However, if someone was going to start a worm bin from scratch, they would probably want to put a layer of damp, shredded newspaper in to get started, with some dead leaves on top. We know that good compost needs to contain a mixture of ‘brown’ and ‘green’ things — sources of carbon and sources of nitrogen. It’s possible that the newspaper doesn’t work as well for the ‘brown’, carbon-containing material as autumn leaves. Kitchen waste is mostly ‘green’ — high in nitrogen. That is why it smells bad when you get too much of it.

It does seem like the way to control mites is to use dry leaves in the bin. This would be easy to do year round if you are able to keep some bagged leaves in your garage or woodshed. If you lived in an apartment, this would be trickier. We don’t know why the leaves help with mites. The bin is quite moist underneath, so it doesn’t seem to be dampness. Perhaps the leaves change the pH and make it an environment that mites don’t do well in.

Harvesting the compost takes a long time and is very labour-intensive. The worms don’t like light but they don’t burrow far into the compost, so even when you just scrape a handful off the surface you have to pick worms and cocoons out of it.

The worm bin doesn’t produce a lot of compost; however, it is very rich. We used some as a top-dressing on the library plants and the geraniums all bloomed very well. The hibiscus began to bloom as well. We also got apple trees and tomato plants germinating in some of the library flower pots!